Conveyance control device and image forming apparatus

ABSTRACT

Provided is a conveyance control device including a driving unit that conveys an object to be conveyed along a predetermined conveyance path, a detection unit that detects a periodic signal for every integer cycle of a cycling member that cycles with following the object to be conveyed which is conveyed along the conveyance path, an acquisition unit that acquires conveyance speed information of the object to be conveyed based on the periodic signal detected by the detection unit and a length of predetermined integer cycles, and a correction unit that corrects an operation timing at which an operation is performed while conveying the object to be conveyed, based on the conveyance speed information acquired by the acquisition unit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2015-025470 filed Feb. 12, 2015.

BACKGROUND Technical Field

The present invention relates to a conveyance control device and an image forming apparatus.

SUMMARY

According to an aspect of the invention, there is provided a conveyance control device including:

a driving unit that conveys an object to be conveyed along a predetermined conveyance path;

a detection unit that detects a periodic signal for every integer cycle of a cycling member that cycles with following the object to be conveyed which is conveyed along the conveyance path;

an acquisition unit that acquires conveyance speed information of the object to be conveyed based on the periodic signal detected by the detection unit and a length of predetermined integer cycles; and

a correction unit that corrects an operation timing at which an operation is performed while conveying the object to be conveyed, based on the conveyance speed information acquired by the acquisition unit.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the present invention will be described in detail based on the following figures, wherein:

FIG. 1 is a schematic diagram of an image forming apparatus according to the present exemplary embodiment;

FIG. 2 is a schematic diagram of an image forming unit according to the present exemplary embodiment;

FIG. 3A is a perspective view of a position detection roller according to the present exemplary embodiment, and FIG. 3B is a front view when seen from an arrow IIIB direction of FIG. 3A;

FIG. 4 is a functional block diagram for performing correction control of an image formation timing according to a conveyance speed variation of a recording medium P on a driving roller in a main controller according to the present exemplary embodiment;

FIGS. 5A to 5C are timing charts illustrating a relationship between a rotation position of a position detection roller and a periodic signal;

FIG. 6 is a flow chart illustrating a flow of an image formation timing correction control routine based on the detection of a conveyance speed according to the present exemplary embodiment;

FIG. 7A is a front view of the position detection roller when plural periodic signals are fetched, and FIG. 7B is a timing chart illustrating a relationship between a rotation position of the position detection roller in FIG. 7A and a periodic signal;

FIGS. 8A to 8C illustrate modification examples of a position detection plate; FIGS. 8A and 8B illustrate a case where a shielding plate is used, and FIG. 8C illustrates a case where a detection mark member and a reflection type sensor are combined with each other;

FIGS. 9A and 9B are functional block diagrams illustrating correction control when a table storage unit storing a correction coefficient for slip compensation is provided;

FIG. 10 is a schematic diagram of an image forming apparatus according to Modification Example 1; and

FIG. 11 is a schematic diagram of an image forming apparatus according to Modification Example 2.

DETAILED DESCRIPTION

FIG. 1 illustrates an outline of an image forming apparatus 10 according to the present exemplary embodiment.

A recording medium P as an example of an object to be conveyed is taken up around a paper feeding roller 16 of a paper feeding unit 14 in the form of a layer in advance. Meanwhile, a typical example of the recording medium P includes a sheet material including paper and a resin film.

The recording medium P taken up around the paper feeding roller 16 is extracted from the outermost layer of the paper feeding roller 16, is wound around plural winding rollers 18, and is sent out to an image forcing unit 20. The recording medium P on which an image is formed by the image forming unit 20 is taken up around a take-up roller 17 of an accommodation unit 15. The take-up roller 17 rotates so as to take up the recording medium F in the form of a layer.

In addition, a portion of the winding roller 18 serves as a driving roller, and is taken up around the take-up roller 17 while adjusting tension of the recording medium P between the rollers.

The image forming apparatus 10 includes a main controller 100. The main controller 100 includes the paper feeding unit 14, the image forming unit 20, a driving control unit 102 of a driving system that controls the driving of a driving system (mainly, a motor) conveying the recording medium P by the accommodation unit 15, and an image forming control unit 104 that acquires image data from the outside, converts the image data to exposure data, and controls an image forming process in the image forming unit 20.

The image forming apparatus 10 of the present invention transfers and fixes a toner image constituted by a developer G (see FIG. 2) to the surface of the recording medium P to thereby form an image on the surface of the recording medium P.

The image forming unit 20 has a function of forming a toner image using the developer G, transferring the toner image to the surface of the recording medium P, and fixing a toner onto the surface of the recording medium P to thereby form an image on the surface of the recording medium P. In the image forming unit 20, image forming units 60C, 60M, 60Y, and 60K are disposed in a vertical direction (height direction of the apparatus) of FIG. 1, and driving rollers 106 and 108 are provided on the upstream side and downstream side of the image forming units 60C, 60M, 60Y, and 60K, respectively, as examples of driving units.

The driving rollers 106 and 108 are configured such that the rotation speeds thereof are independently controlled by the driving control unit 102 of the main controller 100. For example, a conveyance speed according to the driving roller 108 on the downstream side is higher than a conveyance speed according to the driving roller 106 on the upstream side so that tension of the recording medium P during conveyance is maintained within a predetermined range.

The image forming units 60C, 60M, 60Y, and 60K have functions of forming toner images of the respective colors and transferring the toner images of the respective colors to the recording medium P conveyed. The image forming units 60C, 60M, 60Y, and 60K are disposed in this order along a conveyance path of the recording medium P from the upstream side to the downstream side (from top to bottom in FIG. 1) in the conveyance direction of the recording medium P.

Here, a suffix “C” means cyan, a suffix “M” means magenta, a suffix “Y” means yellow, and a suffix “K” means black. The image forming units 60C, 60M, 60Y, and 60K form toner images of a C color, an M color, a Y color, and a K color, respectively. In addition, the image forming units 60C, 60M, 60Y, and 60K have the same configuration except for toner colors included in the developer G used.

Accordingly, an image forming unit 60 will be described in detail with reference to FIG. 2, but the description will be given by omitting the suffixes C, M, Y, and K.

As illustrated in FIG. 2, the image forming unit 60 includes a developer supply unit 70 and a transfer unit 80.

The developer supply unit 70 accommodates the developer G, and has a function of supplying the developer G to the transfer unit 80. The developer supply unit 70 includes a container 72 and a supply roll 74. Meanwhile, a portion of the supply roll 74 is immersed in the developer G accommodated in the container 72.

The container 72 is connected to an external tank (not shown) and is replenished with the developer G stored in the external tank.

The supply roll 14 draws up the developer G accommodated in the container 72 while rotating to thereby supply the developer G to a developing roll 85 to be described later. Here, the layer thickness of the developer G is adjusted by a blade (not shown). The developer is charged to have a positive polarity, as an example, and is supplied to the developing roll 85.

The transfer unit 80 transfers a toner image formed on a photoreceptor 82 to be described later to the recording medium P using the developer G. The transfer unit 80 includes the photoreceptor 82, a charging device 83, an exposure device 84, the developing roll 85, a transfer drum 86, and a transfer roll 88.

The photoreceptor 82 has a function of holding a latent image, and the charging device 83 has a function of charging the photoreceptor 82.

The exposure device 84 has a function of forming a latent image on the photoreceptor 82 charged by the charging device 83, and the developing roll 85 has a function of developing the latent image held by the photoreceptor 82 as a toner image using the developer G supplied from the developer supply unit 70.

The developing roll 85 forms a nip N1 in conjunction with the photoreceptor 82. The developing roll 85 is applied with a voltage while rotating, and develops the latent image held by the photoreceptor 82 as a toner image by using an electric field formed in the nip N1.

The transfer drum 86 has a function of primarily transferring the toner image formed on the photoreceptor 82 to the outer peripheral surface of the transfer drum 86 and holding the transferred toner image. The transfer drum 86 forms a nip N2 in conjunction with the photoreceptor 82. The transfer drum 86 is applied with a voltage while rotating and primarily transfers the toner image on the photoreceptor 82 to the outer peripheral surface thereof by using an electric field formed in the nip N2.

The transfer roll 88 has a function of secondarily transferring the toner image held by the outer peripheral surface of the transfer drum 86 to the recording medium P conveyed. The transfer roll 88 is disposed on the opposite side to the transfer drum 86 with the conveyance path of the recording medium P interposed therebetween and forms a nip N3 in conjunction with the transfer drum 86. The transfer roll 88 is applied with a voltage while rotating and secondarily transfers the toner image held by the outer peripheral surface of the transfer drum 86 to the recording medium P by using an electric field formed in the nip N3.

As illustrated in FIG. 1, a fixing device 90 is provided on the downstream side (downstream side of the driving roller 108) of the image forming unit 60. The fixing device 90 includes a heating roll 92 and a pressure roll 94.

The fixing device 90 has a function of fixing the toner image formed by the image forming unit 60 onto the surface of the recording medium P by heating and pressing toner images of many colors formed on the surface of the recording medium P by the image forming unit 60.

Conveyance Control

Here, in the present exemplary embodiment, the driving of the driving roller 106 provided on the upstream side of the image forming unit 20 and the driving of the driving roller 108 provided on the downstream side are independently controlled by the driving control unit 102 functioning as a portion of the main controller 10 so that a conveyance speed of the recording medium P and the tension (tensioning force) of the recording medium P are controlled within a predetermined range.

The conveyance speed of the recording medium P may become uneven due to factors including expansion and contraction based on physical properties of the recording medium P itself and a slip from a roller which is wound with the recording medium. Such speed unevenness affects distortion at the time of transferring (secondarily transferring) each color.

Consequently, in the present exemplary embodiment, as illustrated in FIG. 1, a conveyance speed detection roller 110 is disposed at the final stags of the image forming unit 60 (between the image forming unit 60K of the K color and the driving roller 108 on the downstream side in the present exemplary embodiment). A rotation state of the conveyance speed detection roller 110 is detected by a position detection sensor 116 to be described later and is fed back to the driving control unit 102 so as to control the rotation speeds of the driving rollers 106 and 108. The conveyance speed detection roller 110 and the position detection sensor 116 function as examples of detection units.

Conveyance Speed Detection Roller 110

As illustrated in FIG. 1, the recording medium P is wound around the conveyance speed detection roller 110. As a result, the conveyance direction of the recording medium F is turned around by 90 degrees from the upper direction to the right direction of FIG. 1. In other words, the recording medium P is wound around one fourth of the whole circumference of the conveyance speed detection roller 110. The conveyance speed detection roller 110 rotates at the same linear speed as the conveyance speed of the recording medium P without slipping between the speed detection roller and the recording medium P by such a winding amount.

Meanwhile, the winding amount which is one fourth of the whole circumference is a criterion of a winding amount that does not cause a slip between the conveyance speed detection roller 110 and the recording medium P, and the winding amount is not limited to a fourth part of the whole circumference.

For example, the winding amount may be increased or decreased in consideration of the physical properties (coefficients of friction) of the conveyance speed detection roller 110 and recording medium P, an installation space (including the volume and spatial shape) of the conveyance speed detection roller 110, and a target conveyance changing angle.

As illustrated in FIGS. 3A and 3B, a position detection plate 114 is attached to a rotation axis 112 of the conveyance speed detection roller 110. The position detection plate 114 in the present exemplary embodiment has a disc shape and rotates centering on the rotation axis 112 (rotates on a concentric circle) in conjunction with the conveyance speed detection roller 110.

A notch portion 114A is formed at one location of a peripheral edge of the position detection plate 114. In addition, the position detection sensor 116 is disposed at one portion of the peripheral edge of the position detection plate 114. In the position detection sensor 116, a pair of leg portions 116B and 116C protrude from a main body portion 116A having a rectangular block shape, and the peripheral edge of the position detection plate 114 passes through a gap between the pair of leg portions 116B and 116C.

As illustrated in FIG. 4, the main body portion 116A of the position detection sensor 116 is provided with a light detection control unit 118. In addition, the leg portion 116B is provided with a light projection unit 120, and the leg portion 116C is provided with a light receiving unit 122. The light detection control unit 118 has a function of performing irradiation with specific light from the light projection unit 20 and outputting an electric signal having been subjected to photoelectric conversion according to whether the light receiving unit 122 receives specific light.

For example, the light detection control unit 118 outputs a low-level signal (L signal, 0 V) when the light receiving unit 122 has not received specific light, and outputs a high-level signal (H signal, 3.3 V or 5.0 V) when the light receiving unit 122 has received specific light. That is, an H signal is output as a pulse signal for each cycle.

Here, as illustrated in FIGS. 3A and 3B, the notch portion 114A is formed in the peripheral edge of the position detection plate 114 as described above. The notch portion 114A passes through the pair of leg portions 116B and 116C whenever the position detection plate 114 rotates one turn. That is, an H signal is output from the position detection sensor 116 whenever the notch portion 114A passes between the pair of leg portions 116B and 116C (whenever the conveyance speed detection roller 110 rotates one turn) (see FIGS. 5A to 5C).

Incidentally, it is premised that the conveyance speed detection roller 110 is concentric with the rotation axis 112 and the position detection plate 114, but the conveyance speed detection roller may be eccentric in the manufacture thereof or due to deterioration over time.

When there is an eccentricity, a speed transmitted to the peripheral surface of the conveyance speed detection roller 110, the rotation axis, and the position detection plate 114 from the recording medium P varies. For example, as illustrated in FIGS. 5A to 5C, a rotational error (eccentricity) of the position detection roller 110 which overlaps the speed of the recording medium may be detected.

That is, a result of the speed detection of the recording medium P in the position detection roller 110 shows that a cycle depending on the speed of the recording medium of FIG. 5A (relatively long cycle, and referred to as “cycle A” below) overlaps a cycle depending on the rotational error of the position detection roller 110 of FIG. 5B (relatively short cycle, and referred to as “cycle B” below) (see FIG. 5C).

On the other hand, from the viewpoint of the above-mentioned color distortion, conveyance may be preferably performed with a target conveyance amount at least at a pitch between colors of the image forming unit 60 (pitch of a secondary transfer position). However, in order to form a peripheral length of the conveyance speed detection roller 110 in compliance with the pitch of the secondary transfer position, more highly accurate manufacture is required than the manufacture of a normal roller.

Consequently, in the present exemplary embodiment, a rotation speed (cycle) for each turn which does not need to take a variation in conveyance speed, occurring when the number of turns of the position detection roller 110 is one or less, into consideration is monitored. That is, in the case of N-round (N is an integer, and N=1 in the present exemplary embodiment) units, even when a rotation speed up to N cycles varies due to the eccentricity of the position detection roller 110 (cycle B), a conveyance length for detecting the rotation speed becomes constant as long as a slip (sliding) does not occur between the position detection roller 110 and the recording medium P, and thus it is possible to obtain an accurate average rotation speed (cycle) for every N cycles.

FIG. 4 is a functional block diagram for performing correction control of an image formation timing, which is targeted for the driving rollers 106 and 108, corresponding to a conveyance speed variation of the recording medium P in the main controller 100. Meanwhile, FIG. 4 does not limit hardware configuration of the main controller 100.

A user interface 150 is connected to the image forming control unit 104 of the main controller 100. The image forming control unit 104 includes an image data processing unit 152 and an image formation execution unit 154.

The image data processing unit 152 has a function of receiving image data from the outside and a function of generating exposure data for each color from the received image data.

The exposure data generated by the image data processing unit 152 is sent out to the image formation execution unit 154. The exposure data is sent out with measuring an image formation timing for each color, and an instruction for conveying the recording medium P at a predetermined conveyance speed is given to the driving control unit 102.

The driving control unit 102 controls driving with respect to each driving roller including the driving rollers 106 and 108. Meanwhile, the driving control unit 102 sends out a signal from a sensor detecting the recording medium P provided at each location of a device to the image forming control unit 104, and controls an image formation time.

The driving control unit 102 is provided with a signal reception unit 156 and is connected to the light detection control unit 118 of the position detection sensor 116. The signal reception unit 156 receives a periodic signal (see FIGS. 5A to 5C) which is output from the light detection control unit 118.

The signal reception unit 156 is connected to a cycle computation unit 158, and the periodic signal received from the light detection control unit 118 is sent out to the cycle computation unit 158. The cycle computation unit 158 computes a rotation cycle of the conveyance speed detection roller 110 based on the periodic signal and sends out the computed rotation cycle to an actual conveyance speed computation unit 160 as an example of an acquisition unit. The actual conveyance speed computation unit 160 computes an actual conveyance speed of the recording medium P based on the peripheral length (length of one turn) of the conveyance speed detection roller 110 and the rotation cycle, and sends out the computed conveyance speed to a difference computation unit 162.

In addition, the actual conveyance speed computation unit 160 sends out a request signal to a target conveyance speed reading unit 164 at a point of time when information of the actual conveyance speed is sent out to the difference computation unit 162.

The target conveyance speed reading unit 164 reads out information of a target conveyance speed of the recording medium P from the image formation execution unit 154 of the image forming control unit 104 based on the request signal, and sends out the information to the difference computation unit 162.

The difference computation unit 162 computes a difference between the information of the actual conveyance speed and the information of the target conveyance speed, and feeds the difference back to an image formation timing correction unit 166, as an example of a correction unit, of the image forming control unit 104.

In the present exemplary embodiment, image formation timings of the other colors (M, Y, and K colors) are corrected based on a C color.

That is, the image formation timing correction unit 166 is connected to the image formation execution unit 154, and sends out information of the correction of the image formation timings of M, Y, and K colors to the image formation execution unit 154 based on the information received from the difference computation unit 162.

The image formation execution unit 154 having received the information of the correction changes the image formation timings of M, Y, and K colors and sends out exposure data to each image forming unit.

For example, when the actual conveyance speed is lower than the target conveyance speed, it takes a long time for the recording medium P to move between the image forming units 60, and thus an image formation timing is delayed.

Hereinafter, operations of the present exemplary embodiment will be described.

Flow of Image Formation

First, a flow of processing for image formation in the image forming apparatus 10 will be described.

When the main controller 100 receives image data, the image data is converted into exposure data of each color, and the converted exposure data of each color is transmitted to the exposure device 84 constituting the image forming unit 60.

Subsequently, in the image forming unit 60, the photoreceptor 82 is charged by a charging device 83C based on an instruction for the execution of image formation, and a charged photoreceptor 82C is exposed by an exposure device 84C, thereby forming a latent image for a C color on the photoreceptor 82C. The latent image for a C color is developed as a toner image of a C color by a developing apparatus 85C supplied with a developer G of a C color from a developer supply unit 70C.

Subsequently, the toner image of a C color reaches the nip N2 by the rotation of the photoreceptor 82C and is primarily transferred to a transfer drum 86C. Further, the toner image of a C color which is transferred to the transfer drum 86C reaches the nip N3 by the rotation of the transfer drum 86C. The toner image of a C color which has reached the nip N3 is secondarily transferred to the surface of the recording medium P conveyed by a transfer roll 88C.

Similarly, in the image forming units 60M, 60Y and 60K constituting the image forming unit 60, the toner images of M, Y, and K colors are secondarily transferred to the surface of the recording medium P from transfer drums 86M, 86Y and 86K in a sequential order so as to overlap the toner image of a C color which is secondarily transferred to the surface of the recording medium P.

Subsequently, the recording medium P having a surface on which the toner image of each color is formed by the image forming unit 60 reaches the fixing device 90. The toner image of each color on the surface of the recording medium P is heated and pressed by a fixing device 90A, and is fixed onto the surface of the recording medium P.

Control of Conveyance Speed

Incidentally, the conveyance speed of the recording medium P may become uneven and affect distortion at the time of transferring (secondarily transferring) each color.

Consequently, in the present exemplary embodiment, the conveyance speed detection roller 110 detecting the conveyance speed of the recording medium P is disposed, and the feed-back control of an image formation timing is performed based on the periodic signal received from the conveyance speed detection roller 110.

Hereinafter, a flow of an image formation timing correction control routine based on the detection of a conveyance speed will be described with reference to a flow chart of FIG. 6.

In step 200, a periodic signal is received from the position detection sensor 116. The periodic signal is a pulse signal which is inverted from an L signal to an H signal for each cycle in the present exemplary embodiment and moves by one turn even when eccentricity occurs in the position detection roller 110. Accordingly, a speed variation in the middle of the movement is offset, and thus the periodic signal may be applied as an accurate periodic signal.

In the subsequent step 202, a cycle t is computed based on the received periodic signal. That is, the cycle is a time between H signals. The time between H signals is theoretically constant all the time, but it is preferable to compute an average value of the times obtained plural times.

Meanwhile, as illustrated in FIGS. 7A and 7B, a cycle may be obtained by forming plural notch portions 114A, 114B, 1140, and 114D in the peripheral edge of the position detection plate 114, individually measuring cycles tn (n is an integer, t1, t2, t3, and t4 in FIG. 7B) of the respective notch portions 114A, 114B, 114C, and 114D, and computing an average value of the cycles. In other words, it is also possible to apply a signal for each slit which is selected from an existing pulse encoder.

In addition, as the number of opportunities to detect a cycle increases (as n of the cycle tn increases) in one turn, it is possible to suspect an error, for example, when an image is formed while accelerating or decelerating the recording medium P.

In the subsequent step 204, a peripheral length L of a position detection roller is read out. Then, the flow chart proceeds to step 206 to compute an actual conveyance speed VJ (average speed) of the recording medium P (VJ=L/t).

In the subsequent step 208, a target conveyance speed VM is read out from the image forming control unit 104. The target conveyance speed VM is a conveyance speed of the recording medium P which, is recognized by the image forming control unit 104. The image formation execution unit 154 of the image forming control unit 104 determines an image formation timing of each color based on the target conveyance speed VM.

In the subsequent step 210, a difference ΔV (=VM−VJ) between the actual conveyance speed VJ and the target conveyance speed VM is computed, and then the flow chart proceeds to step 212.

In step 212, an instruction for the correction of the image formation timing determined based on the target conveyance speed VM is given based on the difference ΔV, and the routine is terminated.

The image formation execution unit 154 of the image forming control unit 104 corrects the image formation timing when an instruction for correction is given. In the present exemplary embodiment, the correction of an image formation timing is performed based on a C color. Hereinafter, the correction of an image formation timing of an M color will be described as an example.

Hereinafter, when an image formation timing is set as tcm, a distance between image formation positions (secondary transfer positions) of Y and M colors is set as Xcm, and a target conveyance speed is set as VM, the image formation timing tcm is normally set by the following Expression (1).

tcm=Xcm/VM  (1)

Here, when there is a difference ΔV between a target conveyance speed VM and an actual conveyance speed VJ, the image formation timing is delayed by Xcm/ΔV when ΔV is positive. Meanwhile, the image formation timing may be advanced when ΔV is negative.

Meanwhile, in the above description, the image formation timing is computed in advance based on the target conveyance speed VM, and correction is performed based on ΔV. However, the image formation timing may be directly computed based on the actual conveyance speed VJ.

Meanwhile, when the image formation timing is computed through correction based on ΔV mentioned above, an image forming process may be performed based on the target conveyance speed VM as an emergency measure even when malfunction of the position detection sensor 116 or the like occurs.

Meanwhile, in the present exemplary embodiment, a circular plate material is used as the position detection plate 114, but light shielding plates 184 and 186 may be provided as illustrated in FIGS. 8A and 8B. In addition, as illustrated in FIG. 8C, a detection mark member 188 may be provided on the peripheral surface of the position detection roller 110, and a signal for each turn may be obtained using a reflection type sensor 190.

Machine Compensation in Manufacture and Installation

When the actual conveyance speed VJ is obtained, a peripheral length L of the position detection roller 110 and a distance (secondary transfer pitch) between image formations of the respective colors have a manufacturing error. Consequently, an image forming process is performed at the time of manufacture or the installation of the image forming apparatus 10, an image formation timing is adjusted through feedback, and a conveyance speed of the recording medium P at that time is set as a target conveyance speed VM, thereby computing the image formation timing. Thereafter, the image formation timing may be corrected based on the difference ΔV between the target conveyance speed VM and the actual conveyance speed VJ.

Temperature Compensation

When the actual conveyance speed VJ is obtained, the peripheral, length L of the position detection roller 110 and the distance (secondary transfer pitch) between image formations of the respective colors may expand or contract and vary due to temperature changes within the apparatus.

In this case, the peripheral length and the distance may be manually adjusted by an operator from the user interface 150. Alternatively, a temperature sensor may be provided in the image forming apparatus 10, and a correction coefficient based on a temperature detected by the temperature sensor may be added to Expression (1) mentioned above. It is preferable that the temperature sensor is located in the vicinity of the position detection roller 110.

Slip Compensation

For example, when a winding amount of the recording medium P with respect to the position detection roller 110 is insufficient due to the space of the image forming apparatus 10, a slip may occur between the position detection roller 110 and the recording medium P. In addition, a minute slip may occur in spite of a sufficient winding amount. It is known that this slip depends on a conveyance speed, and particularly becomes remarkable when an image is formed while accelerating or decelerating the recording medium P.

Consequently, as illustrated in FIGS. 9A and 9B, a table storage unit 192 is provided in the image forming control unit 104, and a relationship between a conveyance speed (actual conveyance speed VJ) and a correction coefficient α based on a slip is tabled in advance and is stored in the table storage unit 192. The correction coefficient may be added to Expression (1) mentioned ahove as a slip correction coefficient when the image formation execution unit 154 computes an image formation timing.

tcm=α×(Xcm/VM)  (2)

FIG. 9B is an example of a table showing an actual conveyance speed VJ and a slip correction coefficient α which is stored in the table storage unit 192.

Modification Example 1

In the present exemplary embodiment, as illustrated in FIG. 1, the image forming apparatus 10 that forms an image on one surface of a recording medium P is illustrated. However, as illustrated in FIG. 10, it is also possible to use a double-surface adaptable image forming apparatus 10R that forms an image on one surface of a recording medium P and then inverts the recording medium P by an inversion device 168 to form an image on the other surface. In this case, the position detection rollers 110, which are disposed in the respective image forming units, may detect an actual conveyance speed VJ independently on the front and back surfaces thereof and may correct an image formation timing independently on the front and back surfaces thereof.

Modification Example 2

In the present exemplary embodiment and Modification Example 1, the electrophotographic image forming apparatus 10 (10R) has been described as an example. However, as illustrated in FIG. 11, it is also possible to use an ink jet type image forming apparatus 10I. Hereinafter, an outline of the ink jet type image forming apparatus 10I will be described.

FIG. 11 illustrates an outline of the ink jet type image forming apparatus 10I according to Modification Example 2 of the present exemplary embodiment (hereinafter, simply referred to as “image forming apparatus 10I”).

The image forming apparatus 10I according to the present exemplary embodiment ejects ink onto a recording medium 12 by a so-called ink jet method using ink to record (print) an image and dries the ink.

As illustrated in FIG. 11, the recording medium P is taken up around a paper feeding roller 171 of a paper feeding unit 170 in the form of a layer in advance.

The recording medium P taken up around the paper feeding roller 171 is extracted from the outermost layer of the paper feeding roller 171, is wound around plural winding rollers 172, and is taken up around a take-up roller 174 of an accommodation unit 173. The take-up roller 174 is provided with a motor (not shown) to rotate the take-up roller 174 so as to take up the recording medium P in the form of a layer.

In FIG. 11, a region for conveyance is provided and serves as an image forming unit 180.

In addition, a region in which the recording medium P is vertically and linearly conveyed is provided on a downstream side of the image forming unit 180 and serves as a drying unit 181.

Ink jet heads 182Y, 182M, 182C, and 182K of yellow (Y), magenta (M), cyan (C), and black (K) colors are arrayed in the image forming unit 180. Hereinafter, the ink jet heads will be collectively referred as an ink jet head 182.

The ink jet head 182 brings ink which is stored in, for example, an ink cassette (not shown) and ejects droplets from nozzles toward a recording medium 12 confronting the nozzles by pressure control, ultrasonic control, or the like.

In the image forming apparatus 10I according to the present exemplary embodiment, nozzles are arrayed in the entire region in a main scanning direction of the recording medium P, the ink jet heads 182 of the respective colors are arrayed in a sub scanning direction of the recording medium P, and droplets having the amount of ink according to image data are ejected from the nozzles of the respective ink jet heads 182 in synchronization with the conveyance speed of the recording medium P.

Meanwhile, this array configuration is not limited, and a configuration may also be adopted in which an ink jet head 27 is moved in a main scanning direction.

In the drying unit 181, the recording medium P on which an image is formed by the image forming unit 180 is conveyed from the top to the bottom of FIG. 11, and surfaces having the respective images formed thereon sequentially confront a dried region in accordance with the conveyance.

The position detection roller 110 is provided on the downstream side of a driving roller 176 of the image forming apparatus 10I and on the upstream side of the image forming unit 180, and the recording medium P is wound around the position detection roller.

Similarly to FIGS. 3A and 3B, the position detection roller 110 is provided with the position detection plate 114 and is disposed corresponding to the position detection sensor 116.

The position detection sensor 116 outputs a pulse signal (H signal) for each turn in association with the conveyance of the recording medium P, and controls (corrects) an image formation timing in the image forming unit 180 based on the periodic signal thereof.

The foregoing description of the exemplary embodiments of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents. 

What is claimed is:
 1. A conveyance control device comprising: a driving unit that conveys an object to be conveyed along a predetermined conveyance path; a detection unit that detects a periodic signal for every integer cycle of a cycling member that cycles with following the object to be conveyed which is conveyed along the conveyance path; an acquisition unit that acquires conveyance speed information of the object to be conveyed based on the periodic signal detected by the detection unit and a length of predetermined integer cycles; and a correction unit that corrects an operation timing at which an operation is performed while conveying the object to be conveyed, based on the conveyance speed information acquired by the acquisition unit.
 2. An image forming apparatus comprising: a driving unit that conveys a recording medium along a predetermined conveyance path; a detection unit that detects a periodic signal for every integer cycle of a cycling member that cycles with following the recording medium which is conveyed along the conveyance path; an acquisition unit that acquires conveyance speed information of the recording medium based on the periodic signal detected by the detection unit and a length of predetermined integer cycles; an image forming unit that is provided so as to confront the conveyance path and forms an image on the recording medium; an estimation unit that estimates a conveyance speed of the recording medium conveyed through an image formation region in the image forming unit, based on the conveyance speed information of the recording medium which is acquired by the acquisition unit; and an image formation timing correction unit that corrects a timing when an image is formed by the image forming unit, based on the conveyance speed of the recording medium in the image formation region which is estimated by the estimation unit.
 3. The image forming apparatus according to claim 2, wherein the image forming unit forms one image formed as two or more images are superimposed on each other at a location shifted in a conveyance direction in the image formation region, and the image formation timing correction unit corrects a timing when an image is formed by the image forming unit so as to perform registration of images formed at respective locations.
 4. The conveyance control device according to claim 1, wherein the detection unit has a plurality or opportunities for performing detection while the cycling member rotates one turn. 5 The image forming apparatus according to claim 2, wherein the detection unit has a plurality of opportunities for performing detection while the cycling member rotates one turn. 